Abstract

The influence of random vibrations on the performance of a dynamic phase-shifting speckle pattern interferometer is investigated by means of experiments and numerical simulations. Two aspects are evaluated: first, temporal unwrapping reliability, second, vibration-induced phase noise. The former is found to be a significant constraint, even for peak velocities well below the Nyquist velocity limit of the interferometer. Shorter sampling windows and higher framing rates are shown to increase the unwrapping success rate, but longer windows reduce the phase error. Three analytical criteria for determining the expected unwrapping success rate are proposed and compared.

Detail of the unwrapped phase change measured at different locations of a disk submitted to piston random vibration for a rms displacement amplitude of σz = λ/4. Each curve corresponds to a phase of pixel clusters with a different starting phase. The mean phase over all the clusters is also shown in bold.

(a) Velocity of a surface excited with a random vibration with a rms phase amplitude of π/2 rad. Modulus, in arbitrary units, calculated from the windowed Fourier transform of the intensity signal by use of a Hanning window (b) with M = 32; (c) with M = 64. The framing rate of the camera corresponds to 1 kHz.

(a) Velocity of a surface excited with a random vibration with an rms phase amplitude of 2π rad. Modulus, in arbitrary units, calculated from the windowed Fourier transform of the intensity signal by using a Hanning window (b) with M = 32; (c) with M = 64. The framing rate of the camera corresponds to 1 kHz.